<!DOCTYPE html>
<html>

<head>
<title>Assignment 4 Picture Cube</title>
<meta http-equiv="content-type" content="text/html; charset=ISO-8859-1">

<script type="text/javascript" src="glMatrix-0.9.5.min.js"></script>
<script type="text/javascript" src="webgl-utils.js"></script>

<script id="shader-fs" type="x-shader/x-fragment">
	#ifdef GL_ES
	precision highp float;
	#endif
	
	uniform sampler2D front;
        uniform sampler2D back;
        uniform sampler2D top;
        uniform sampler2D bottom;
        uniform sampler2D right;
        uniform sampler2D left;

        varying vec2 vTextureCoord;
        varying float vFace;

        void main(void) {
		if (vFace < 0.1)
			gl_FragColor = texture2D(front, vTextureCoord);
		else if (vFace < 1.1)
			gl_FragColor = texture2D(back, vTextureCoord);
		else if (vFace < 2.1)
			gl_FragColor = texture2D(top, vTextureCoord);
		else if (vFace < 3.1)
			gl_FragColor = texture2D(bottom, vTextureCoord);
		else if (vFace < 4.1)
			gl_FragColor = texture2D(right, vTextureCoord);
		else
			gl_FragColor = texture2D(left, vTextureCoord);
	}
</script>

<script id="shader-vs" type="x-shader/x-vertex">	
	attribute vec3 aVertexPosition;
	attribute vec2 aTextureCoord;
	attribute float aFace;
	
	uniform mat4 uMVMatrix;
	uniform mat4 uPMatrix;

	varying vec2 vTextureCoord;
	varying float vFace;

	void main(void) {
		gl_Position = uPMatrix * uMVMatrix * vec4(aVertexPosition, 1.0);
		vTextureCoord = aTextureCoord;
		vFace = aFace;
	}	
</script>

<script type="text/javascript">

	var gl;

	function initGL(canvas) {
		try {
			gl = canvas.getContext("experimental-webgl");
			gl.viewportWidth = canvas.width;
			gl.viewportHeight = canvas.height;
		} catch (e) {
		}
		if (!gl) {
			alert("Could not initialise WebGL, sorry :-(");
		}
	}

	function getShader(gl, id) {
		var shaderScript = document.getElementById(id);
		if (!shaderScript) {
			return null;
		}

		var str = "";
		var k = shaderScript.firstChild;
		while (k) {
			if (k.nodeType == 3) {
				str += k.textContent;
			}
			k = k.nextSibling;
		}

		var shader;
		if (shaderScript.type == "x-shader/x-fragment") {
			shader = gl.createShader(gl.FRAGMENT_SHADER);
		} else if (shaderScript.type == "x-shader/x-vertex") {
			shader = gl.createShader(gl.VERTEX_SHADER);
		} else {
			return null;
		}

		gl.shaderSource(shader, str);
		gl.compileShader(shader);

		if (!gl.getShaderParameter(shader, gl.COMPILE_STATUS)) {
			alert(gl.getShaderInfoLog(shader));
			return null;
		}

		return shader;
	}

	var shaderProgram;

	function initShaders() {
		var fragmentShader = getShader(gl, "shader-fs");
		var vertexShader = getShader(gl, "shader-vs");

		shaderProgram = gl.createProgram();
		gl.attachShader(shaderProgram, vertexShader);
		gl.attachShader(shaderProgram, fragmentShader);
		gl.linkProgram(shaderProgram);

		if (!gl.getProgramParameter(shaderProgram, gl.LINK_STATUS)) {
			alert("Could not initialise shaders");
		}

		gl.useProgram(shaderProgram);

		shaderProgram.vertexPositionAttribute = gl.getAttribLocation(shaderProgram, "aVertexPosition");
		gl.enableVertexAttribArray(shaderProgram.vertexPositionAttribute);

		shaderProgram.textureCoordAttribute = gl.getAttribLocation(shaderProgram, "aTextureCoord");
		gl.enableVertexAttribArray(shaderProgram.textureCoordAttribute);

		shaderProgram.textureLookUpAttribute = gl.getAttribLocation(shaderProgram, "aFace");
		gl.enableVertexAttribArray(shaderProgram.textureLookUpAttribute);

		shaderProgram.pMatrixUniform = gl.getUniformLocation(shaderProgram, "uPMatrix");
		shaderProgram.mvMatrixUniform = gl.getUniformLocation(shaderProgram, "uMVMatrix");

		shaderProgram.front = gl.getUniformLocation(shaderProgram, "front");
		shaderProgram.back = gl.getUniformLocation(shaderProgram, "back");
		shaderProgram.top = gl.getUniformLocation(shaderProgram, "top");
		shaderProgram.bottom = gl.getUniformLocation(shaderProgram, "bottom");
		shaderProgram.right = gl.getUniformLocation(shaderProgram, "right");
		shaderProgram.left = gl.getUniformLocation(shaderProgram, "left");
	}
		
	var leftTexture;
	var rightTexture;
	var topTexture;
	var bottomTexture;
	var frontTexture;
	var backTexture;
	
	var texturesToLoad = 6;	
	
	function createTextureFromImage(image, offset, uniform) {
		var texture = gl.createTexture();		
		gl.bindTexture(gl.TEXTURE_2D, texture);
		gl.pixelStorei(gl.UNPACK_FLIP_Y_WEBGL, true);		
		gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, gl.RGBA, gl.UNSIGNED_BYTE, image);
		if (isPowerOfTwo(image.width) && isPowerOfTwo(image.height)){
			gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.NEAREST);
			gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.NEAREST);
		}else{
			gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.LINEAR);
			gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_S, gl.CLAMP_TO_EDGE);
			gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_T, gl.CLAMP_TO_EDGE);
		}
			
		texturesToLoad--;
			
		gl.bindTexture(gl.TEXTURE_2D, null);
		return texture;
	}
	
	function initTextures() {
	
		// Its best if your image width, height are a power of two
		// Update this with your images, and update your location claim text below:
		// 	Alex - top, right
		//   Kayla - front, bottom
		var textureImages = [
			{ 
				src : "colored.jpg",
				loc : "front"
			},
			{
				src : "hetcher1.jpg",
				loc : "back"
			},
			{
				src : "smurfette.jpg",
				loc : "top"
			},
			{
				src : "gradient.jpg",
				loc : "bottom"
			},
			{
				src : "lightning.jpg",
				loc : "left"
			},
			{
				src : "80085.jpg",
				loc : "right"
			}
		];
		
		// load all the textures
		var i, image;
		for (i in textureImages) {
			image = new Image();
			image.cubeFace = textureImages[i].loc;
			image.onload = function() {
				eval(this.cubeFace+"Texture = createTextureFromImage(this, 0, shaderProgram."+this.cubeFace+");");
			}
			image.src = textureImages[i].src;
		} // for 
	}

	function setMatrixUniforms() {
		gl.uniformMatrix4fv(shaderProgram.pMatrixUniform, false, pMatrix);
		gl.uniformMatrix4fv(shaderProgram.mvMatrixUniform, false, mvMatrix);
	}

	function degToRad(degrees) {
		return degrees * Math.PI / 180;
	}

	function isPowerOfTwo(value) {
		return ((value & (value - 1)) == 0);
	}

	var cubeVertexPositionBuffer;
	var cubeVertexTextureCoordBuffer;
	var cubeVertexIndexBuffer;
	var textureLookUpBuffer;
	
	function initBuffers() {
		cubeVertexPositionBuffer = gl.createBuffer();
		gl.bindBuffer(gl.ARRAY_BUFFER, cubeVertexPositionBuffer);
		vertices = [
			// Front face
			-1.0, -1.0,  1.0,
			1.0, -1.0,  1.0,
			1.0,  1.0,  1.0,
			-1.0,  1.0,  1.0,

			// Back face
			-1.0, -1.0, -1.0,
			-1.0,  1.0, -1.0,
			1.0,  1.0, -1.0,
			1.0, -1.0, -1.0,

			// Top face
			-1.0,  1.0, -1.0,
			-1.0,  1.0,  1.0,
			1.0,  1.0,  1.0,
			1.0,  1.0, -1.0,

			// Bottom face
			-1.0, -1.0, -1.0,
			1.0, -1.0, -1.0,
			1.0, -1.0,  1.0,
			-1.0, -1.0,  1.0,

			// Right face
			1.0, -1.0, -1.0,
			1.0,  1.0, -1.0,
			1.0,  1.0,  1.0,
			1.0, -1.0,  1.0,

			// Left face
			-1.0, -1.0, -1.0,
			-1.0, -1.0,  1.0,
			-1.0,  1.0,  1.0,
			-1.0,  1.0, -1.0,
		];
		gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(vertices), gl.STATIC_DRAW);
		cubeVertexPositionBuffer.itemSize = 3;
		cubeVertexPositionBuffer.numItems = 24;

		cubeVertexTextureCoordBuffer = gl.createBuffer();
		gl.bindBuffer(gl.ARRAY_BUFFER, cubeVertexTextureCoordBuffer);
		var textureCoords = [
			// Front face
			0.0, 0.0,
			1.0, 0.0,
			1.0, 1.0,
			0.0, 1.0,

			// Back face
			1.0, 0.0,
			1.0, 1.0,
			0.0, 1.0,
			0.0, 0.0,

			// Top face
			0.0, 1.0,
			0.0, 0.0,
			1.0, 0.0,
			1.0, 1.0,

			// Bottom face
			1.0, 1.0,
			0.0, 1.0,
			0.0, 0.0,
			1.0, 0.0,

			// Right face
			1.0, 0.0,
			1.0, 1.0,
			0.0, 1.0,
			0.0, 0.0,

			// Left face
			0.0, 0.0,
			1.0, 0.0,
			1.0, 1.0,
			0.0, 1.0,
		];
		gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(textureCoords), gl.STATIC_DRAW);
		cubeVertexTextureCoordBuffer.itemSize = 2;
		cubeVertexTextureCoordBuffer.numItems = 24;

		textureLookUpBuffer = gl.createBuffer();
		gl.bindBuffer(gl.ARRAY_BUFFER, textureLookUpBuffer);
		var lookUpArray = [
			// Front face
			0.0, 0.0, 0.0, 0.0, 
 
			// Back face
			1.0, 1.0, 1.0, 1.0, 
				
			// Top face
			2.0, 2.0, 2.0, 2.0, 

			// Bottom face
			3.0, 3.0, 3.0, 3.0, 

			// Right face
			4.0, 4.0, 4.0, 4.0, 

			// Left face
			5.0, 5.0, 5.0, 5.0
		];
		gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(lookUpArray), gl.STATIC_DRAW);
		textureLookUpBuffer.itemSize = 1;
		textureLookUpBuffer.numItems = 24;

		cubeVertexIndexBuffer = gl.createBuffer();
		gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, cubeVertexIndexBuffer);
		var cubeVertexIndices = [
			0, 1, 2,		0, 2, 3,    		// Front face
			4, 5, 6,      	4, 6, 7,    		// Back face
			8, 9, 10,     	8, 10, 11,  	// Top face
			12, 13, 14,   	12, 14, 15, 	// Bottom face
			16, 17, 18,   	16, 18, 19, 	// Right face
			20, 21, 22,   	20, 22, 23  	// Left face
		];
		gl.bufferData(gl.ELEMENT_ARRAY_BUFFER, new Uint16Array(cubeVertexIndices), gl.STATIC_DRAW);
		cubeVertexIndexBuffer.itemSize = 1;
		cubeVertexIndexBuffer.numItems = 36;
	}

	var mvMatrix = mat4.create();    
	var pMatrix = mat4.create();
    
	var xRot = 0;
	var yRot = 0;
	var zRot = 0;

	function drawScene() {
		gl.viewport(0, 0, gl.viewportWidth, gl.viewportHeight);
		gl.clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT);

		mat4.perspective(45, gl.viewportWidth / gl.viewportHeight, 0.1, 100.0, pMatrix);

		mat4.identity(mvMatrix);

		mat4.translate(mvMatrix, [0.0, 0.0, -5.0]);

		mat4.rotate(mvMatrix, degToRad(xRot), [1, 0, 0]);
		mat4.rotate(mvMatrix, degToRad(yRot), [0, 1, 0]);
		mat4.rotate(mvMatrix, degToRad(zRot), [0, 0, 1]);
		
		gl.bindBuffer(gl.ARRAY_BUFFER, cubeVertexPositionBuffer);
		gl.vertexAttribPointer(shaderProgram.vertexPositionAttribute, cubeVertexPositionBuffer.itemSize, gl.FLOAT, false, 0, 0);
			
		gl.bindBuffer(gl.ARRAY_BUFFER, cubeVertexTextureCoordBuffer);
		gl.vertexAttribPointer(shaderProgram.textureCoordAttribute, cubeVertexTextureCoordBuffer.itemSize, gl.FLOAT, false, 0, 0);
			
		gl.bindBuffer(gl.ARRAY_BUFFER, textureLookUpBuffer);
		gl.vertexAttribPointer(shaderProgram.textureLookUpAttribute, textureLookUpBuffer.itemSize, gl.FLOAT, false, 0, 0);
			
		gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, cubeVertexIndexBuffer);
			
		// all textures have been loaded, first time
		if (texturesToLoad == 0){
			gl.activeTexture(gl.TEXTURE0 + 0);
			gl.bindTexture(gl.TEXTURE_2D, frontTexture);
			gl.uniform1i(shaderProgram.front, 0); 
			
			gl.activeTexture(gl.TEXTURE0 + 1);
			gl.bindTexture(gl.TEXTURE_2D, backTexture);
			gl.uniform1i(shaderProgram.back, 1); 
			
			gl.activeTexture(gl.TEXTURE0 + 2);
			gl.bindTexture(gl.TEXTURE_2D, topTexture);
			gl.uniform1i(shaderProgram.top, 2); 
			
			gl.activeTexture(gl.TEXTURE0 + 3);
			gl.bindTexture(gl.TEXTURE_2D, bottomTexture);
			gl.uniform1i(shaderProgram.bottom, 3); 
			
			gl.activeTexture(gl.TEXTURE0 + 4);
			gl.bindTexture(gl.TEXTURE_2D, rightTexture);
			gl.uniform1i(shaderProgram.right, 4); 
			
			gl.activeTexture(gl.TEXTURE0 + 5);
			gl.bindTexture(gl.TEXTURE_2D, leftTexture);
			gl.uniform1i(shaderProgram.left, 5); 
				
			// This block only needs to run once
			texturesToLoad--;
		}
			
		setMatrixUniforms();
		gl.drawElements(gl.TRIANGLES, cubeVertexIndexBuffer.numItems, gl.UNSIGNED_SHORT, 0);
	}

	var lastTime = 0;

	function animate() {
		var timeNow = new Date().getTime();
		if (lastTime != 0) {
			var elapsed = timeNow - lastTime;

			xRot += (90 * elapsed) / 1000.0;
			yRot += (90 * elapsed) / 1000.0;
			zRot += (90 * elapsed) / 1000.0;
		}
		lastTime = timeNow;
	}

	function tick() {
		requestAnimFrame(tick);
		drawScene();
		animate();
	}

	function webGLStart() {
		var canvas = document.getElementById("theCanvas");
		initGL(canvas);
		initShaders();
		initBuffers();
		initTextures();

		gl.clearColor(0.0, 0.0, 0.0, 1.0);
		gl.enable(gl.DEPTH_TEST);

		tick();
	}

</script>
</head>


<body onload="webGLStart();">
	<div>
		<canvas id="theCanvas" style="border: none;" width="500" height="500"></canvas>
	</div>
</body>

</html>
